# extend
class Father1:
    def f1(self):
        print('Father1: f1 def')

class Father2:
    def f1(self):
        print('Father2: f1 def')
    def f2(self):
        print('Father2: f2 def')

class Son(Father2, Father1):
    def s1(self):
        print('Son1: def')

if __name__ == '__main__':
    s = Son()
    s.f1()
    s.f2()
    s.s1()
